The National Institutes of Health desires to have more economical methods to produce 18-labeled oxygen for use in energy expenditures studies and body composition studies. Traditionally, the oxygen isotope is produced through cryogenic distillation of nitric oxide culminating in an energy intensive and large process. An alternative process is proposed by Reactive Innovations, LLC to electrochemically generate 18-labeled oxygen via the electrolysis of doubly labeled water. During a Phase I program, a production system will be developed that can produce 18-labeled oxygen on-site and on-demand in a compact generator. This production system will consist of a compact water electrolyzer packaged into a desktop unit that will process doubly labeled water. The innovation in this work is an inexpensive electrolysis cell that Reactive Innovations has developed for high-pressure gas generation and water disinfection systems. Processing doubly labeled water in the cell produces an 18- labeled oxygen isotope that can subsequently be stored on-site or used directly in energy expenditure studies. A follow-on effort will package this generator into fieldable units. PUBLIC HEALTH RELEVANCE: The relevance of this new 18-labeled oxygen production system is to enable researchers and the medical community a convenient and economical system to produce this oxygen isotope on-site and on-demand. This will enable the isotope to be stored for subsequent use or to be used directly for energy expenditure studies or body composition studies. The compact size of the 18-labeled oxygen production system will result in an economical system that quickly and inexpensively produces the oxygen isotope from just a source of doubly labeled water.